DE2340604C2 - - Google Patents

Description

The invention relates to a catalyst with a vice him bender and protective against mechanical damage porous Coating of sintered inorganic material, available by applying the coating to the catalyst under Er overheat.

Such a catalyst is known from US-PS 30 30 300 be known. It is on a solid core of catalyst formed a discontinuous glass coating, the firmly adheres to the core material and the abrasion resistance of the Kerns improved. The glass coating is on the other hand extremely thin and therefore contributes only slightly to the structural Integrity of the catalyst body at. The well-known Catalyst structure is thus be use cases limited, in which the catalyst material in the form of Gra nulatkörpern is present with sufficiently high strength and whereby also during a continuous use of Ka talysators not the initial strength of the granules is significantly impaired.  

In some applications, however, is the catalyst in powder form, or it comes in the application of kata lysators to a Pulverisierungsseffekt the beginning of the Application present granules. Such a powder The effect of this effect is on practical industrial applications Use of the catalyst to problems, and it is therefore äu very important, the disadvantages of pulverization of Granu to avoid latkörkörner the catalyst.

Object of the present invention is thus the creation a largely protected against mechanical destruction Catalyst, in granular form or as pulverisable Granules or in powder form may be present.

This object is achieved by a catalyst of the type mentioned solved in that a catalyst coated with a combustible organic material or that a powdered catalyst with a combustible mixed organic material and then shaped is that the product obtained with a burnable organic material, an inorganic powder and given optionally a binder containing coating material be is layered and that the coated product on a for Sintering or melting the powdery inorganic Ma terials and optionally the binder and Ver burning the combustible organic material sufficiently high temperature is heated.

The catalyst according to the invention has a porous coating with a variety of fine passes on. The micropores in the coating serve to the catalyst for the gaseous or to make liquid medium accessible. Such a Catalyst has a high compressive strength, Schlagfe Strength and abrasion resistance and is thus in the application  not pulverized. In particular, the coating does not destroyed when the volume of the catalyst by heating or reaction is increased, in particular, the cataly manganese oxide, which is used to prepare alkylphe nolen from phenol and methanol serves.

The catalyst to be protected may be in pure form or in the form a mixture with an inert material or on a Trä germaterial upset. The catalyst of the invention is by granulation of the catalyst to be protected and coating the Granules with a coating mass and subsequent Sintering of the coated product. in this connection a coating with fine passages is formed.

One can use a catalyst according to the invention, which as Kern a powdery catalyst with a large surface area characterized, thereby producing that the powdery Ka a catalyst with a combustible organic powder mix and coat this mixture with the coating and Afterwards the whole thing sinters, whereby the combustible organic Substance burns. In addition, it is possible between to provide a space for the core and the coating by one granules first with a combustible organic Coated powder and then applying the coating, the whole thing with combustion of the organic powder is sintered.

As catalyst, the most diverse pul come deformed or granular catalysts  in question. In particular, the catalyst can one during application or regeneration slightly mechanical in air or chemically destructible substance, such as manganese oxide, which is used to prepare alkylphenol from phenol and methanol serves. The catalyst may be a mixture of consist of two or more catalytically active components. The catalytic active component can be added to a substrate be brought, if z. B. as such platinum, Palladium or another expensive component is used.

An advantage of the invention is a carrier with a to use relatively low strength can. The combustible organic material used to form an intermediate space between the core and the coating serves, can be a coal hydrate material, such as cellulose, sawdust, fibers or walnut cup powder or a combustible polymer, such as As a polyolefin or a polystyrene. In the combustible organic Ma terial is a material used in sintering burns. Furthermore, the material for forming a Space can also be used in the plating Provide micro-passages. It is particularly preferred microcrystalline cellulose or derivatives thereof, wheat to use flour or cornstarch. As coating materials come inorganic powder in question, such as molten alumi oxide, silicon carbide, alumina, silica, Zirconium or zirconium oxide and glass powder, such as sodium  glass, leaded glass or borosilicate glass or metal powder such as iron, aluminum, copper, tin, lead, zinc or alloy powder, such as stainless steel or bronze, magnesium oxide, Cement, such as Portland cement or aluminum cement.

It is possible in particular to choose a covering material which is similar to an activity that of the catalyst. If z. B. Magnesium oxide mainly as a coating material for Her position of a catalyst for alkylphenol formation is used, it is observed that at high temperatures also the magnesium oxide itself has a catalytic activity unfolded. Certain coating materials can be sintered, hardened or hardened, at the touch place, such as As copper powder, glass powder, alumina cement or Portland cement. Most of the coating materials However, they are too hard for sintering or setting Accordingly, in these cases it is preferable to add a binder, which melts or softens by heating and sinters or the powdery coating material binds. Come as a binder Clay, kaolin, feldspar or glass powder in question.

In many cases, the temperature for sintering, Melting or curing in the range of about 400-1400 ° C. It is preferred to prior to sintering, setting or hardening the coating material to add a binder. One can make the desired pores in the coating, by burning a combustible organic material, such as whale nutshell powder, fibers or sawdust admixed and burns these materials during sintering.  

The coating should have the following characteristics in particular respectively:

• 1) The coating should have a sufficiently high strength have, so that a disintegration of the powdered catalyst in practical An Use by impact or abrasion is avoided. When the compressive strength with a Hardness tester (cracking) is measured, so you put found that the compressive strength of the coating of the dimensions and depends on use and preferably above 3 kg / cm² and in particular above 7 kg / cm². The compressive strength of the coating may be greater than the fatigue strength at every application.
• 2) The coating has a multiplicity of micropores, which are formed as passages and a connection from the catalyst to be protected to the outer surface. This Mirko pores are formed by sintering the one herge combustible organic material containing coating material provides. These are not closed holes or cells like porcelain, but pores, which are enough are far, so that gas molecules or liquid molecules from the outer surface of the coating to the core forming one Catalyst can penetrate. The diameter of the fine pores can be measured by a porosimeter and is usually 0.05-1000 μm, preferably 0.5-500 μm and especially at 1-100 microns. The pores preferably run transversely so that the catalyst is within the coating  remains. It is preferred to number the micropores to train rich and big as possible. The apparent Porosity is usually in the range of 20-70%, preferably 30-65%. The measurements were made according to the Japanese Industrial Standard JIS R 2205 (1955). The pore volume measured with the porosimeter is usually in the range of 0.01-0.7 cc / g and especially in Range of 0.02-0.6 cc / g.

The thickness of the coating depends on the required strength and the size of the micropores. When increasing the thickness increases in strength, but decreases in this case the proportion of the catalyst and the flow resistance is increased by the coating. Accordingly, the aim is to choose the thickness of the coating so that a sufficient strength is achieved. The relationship the thickness of the coating to the inner diameter of the coating is usually in the range of 5-100%, preferably 6-50% and in particular 8-20%.

The type and amount of catalyst, the type and Amount of coating material, the type and amount of binder, the thickness of the coating, the particle size and the ratio the catalyst to the coating and the porosity the coating, the diameter of the fine pores and the pores Volumes can be selected as desired. If the Catalyst is relatively cheap, such as activated carbon or Manganese oxide and granulated without carrier material can be is the proportion of catalyst is very high. On the other hand, if the catalytic active substance is expensive, and if a carrier material with this substance is loaded or mixed with this substance, so can the amount of active substance quite low and the Proportion of the carrier material to be very large. In the latter  Case, the carrier may be a powder or a powder Be material.

The particle diameter depends on the conditions of use, for example, from the packing of the column and is usually in the range from 1-25 mm. Within the coating, the catalyst can be powdery. If between the catalyst in the core and the coating is a gap, so The coating does not break when the core is thermally expands. If manganese oxide is used as the catalyst, so there is a change in volume when treated with air for the purpose of the rengeneration. In this case it is advantageous that between the core and the coating a gap is provided, so that the life of the material also at repeated regeneration is long enough. In general it is always desirable to provide a gap when the volume change of the catalyst through the heat or by chemical reaction is great. The catalyst can remain in the coating and you can the same or a different catalyst Add cover material. In general, the addition of the Catalyst for coating material in the manner  made that after formation of the coating an impregnation nierung with the additional catalyst and a subsequent activation.

The catalyst according to the invention can be prepared by the use of conventional Licher granulation can be produced. For example, a mixture of to be protected Catalyst and a suitable combustible granulated organic material and water in paste form by adding a water-kneaded mixture  extruded or by adding the paste granulated, z. B. in a granulator for Her position of spherical grains slices granulator or rotary disk granulator. The mixture the catalyst and a suitable Zusatzma terials is being tabletted and granulated. The grains obtained are placed in a granulator, such. B. a plate granulator or a turntable granulator, and with the coating material if necessary coated under the spray of water. Also, it is possible the Grains with the coating material by a printing process to coat. For a special coating process become the grains with an up Mixture mixed and then the mixture by spray drying dried. The coating method can be free to get voted. However, it is preferred to have the grains in one Plate granulator or a turntable granulator to be layers to achieve a uniform thickness of the coating. When the combustible organic material, e.g. B. the Cellulosic material, saccharide or polyvinyl alcohol Coating with the coating material in the same way as applied to the coating with the coating material is, so it is possible, between the coating and the core material to provide a gap. If that burns bare organic material with the catalyst it is possible to intermediate in the core body provide space. The formation of the gap prevents a destruction of the coating by a change in volume of Core material. Furthermore, this is the surface of the Core material increased. The obtained coated particles are heated to sinter the coating or to set to bring and the combustible organic material to burn, leaving a stable composite Grain with a variety of pores is formed and further  the catalyst is activated. Usually the particles obtained become less than 200 ° C dried, then placed in a jar and gradually heated in the oven. The speed of the temperature increase is reduced upon reaching the decomposition temperature, so that the combustible organic material burns completely. Thereafter, the product becomes the predetermined final temperature held for several hours. The sintering conditions depend on the required composition. to Activation of the catalyst is sometimes necessary to treat this with a suitable gas, such as With nitrogen or hydrogen. This ge preferably happens simultaneously with the formation of the Coating or after formation of the coating. If it is not wishes is the catalyst with a specific To treat medium like water, it will be granulated functional material coated with a saccharide and then coated with the coating material, whereupon the Saccharide during sintering of the coating material is burned away.

There may also be other methods of granulation and sinte be selected. For example, a catalyst may be there be prepared by mixing a mixture of manganese dioxide and ferric oxide granulated with a mixture coated with alumina powder and a glass binder and then the coated product to form a coating sinters. Such a catalyst is suitable as Oxyda tion catalyst for the oxidation of carbon monoxide or carbon hydrogen in exhaust gases of internal combustion engines.  

example 1

100 parts of manganese oxide prepared by heating by electro lytic manganese oxide at 1000 ° C, and 5 parts of wheat starch as well a small amount of water is mixed and carried kneads. The mixture is placed in a rotary disk granulator given and granulated under the spray of water. The Granules are further in the granulator under introduction of Water treated, with spherical granules of be be made of a certain size. A coating material is by mixing and kneading 80 parts of molten Alumina (120 mesh per 2.54 cm) and a binder in the form of 15 parts kaolin, 5 parts feldspar, 5 parts wheat starch and 20 parts of water. The spherical granules be in the granulator while spraying water and further treated with the addition of the coating material, wherein a coating of predetermined thickness is formed. The coated one Product is dried at 80-120 ° C and then in a Vessel is given, which is inserted into an oven. thereupon the temperature gradually changes from 250 ° C to 600 ° C and over heated to 1200 ° C. The product is left for 3 h at 1200 ° C, so that a material with a stable coating and with a variety of fine passes is obtained.

The catalyst obtained consists of spherical Granules with a core of manganese oxide and with a diameter of 5 mm and with a coating of porous Aluminum oxide with a thickness of 0.5 mm and a Diameter of 6.0 mm. He had the physical properties listed below:

The diameter, the pore volume and the apparent porosity of the coating are applied to the coating material after removal of the core material measured by crushing the sample. The same measurements are performed on other pores.

Compressive strength | 11.0 kg average pore diameter 20-50 μm Pore volume coating 0.249 cc / g apparent porosity of the coating 45.0%

Using this catalyst becomes phenol reacted with methanol under the following conditions:

Phenolpartialdruck 0.0803 atmospheres methanol partial 0.803 atmospheres nitrogen partial 0.1164 atmospheres Raumgeschwindgkeit 442 h ^-1 reaction temperature 400 ° C

Results 4 h after the beginning of the reaction Conversion of phenol | 96.7% Yield of 2,6-xylenol 93.4% Yield of O-cresol 3.3%

The compressive strength of the catalyst after 50 h reaction time is 10.0 kg. Upon further reaction, the pressure solid decreases not off. These results clearly show that the invent The catalyst according to the invention has sufficient strength and a has sufficient activity; although the manganese oxide is powdery is, it is not lost.

Comparative example

Manganese oxide is granulated and not ver coated see and then used for the same reaction. The obtained by heat treatment according to Example 1 manganese oxide becomes 5 mm grains knife and 5 mm in height and then at 1200 ° C sintered. The resulting catalyst becomes through  leadership of the reaction used in Example 1.

5 hours after the start of the reaction, the following results receive:

Conversion of phenol | 98.5% Yield of 2,6-xylenol 86.0% Yield of O-cresol 12.5% Compressive strength of the catalyst before the reaction 25.9 kg (per 5 cm length) after 50 h reaction 0 kg

The catalyst is converted to powder during the reaction and is therefore not suitable for the practical Ge consumption.

example 2

60 parts alumina (120 mesh per 2.54 cm) and a binder of 40 parts glass powder (400 mesh per 2.54 cm) and 5 parts Wheat starch and 15 parts of water are mixed and ge kneads. The granules according to Example 1 are with a Turning disk granulator with this material under spraying coated with water and with the addition of the material. To the coating to a predetermined thickness is the be layered material dried at 80-120 ° C and in a Ge and in the oven gradually from 250 ° C to 600 ° C he hitzt. The product is sintered for 3 h at 750 ° C, wherein a stable coating with a variety of fine passages is obtained. The resulting grains have spherical Ge stalt and the inside of the granules becomes powdery Manganese oxide formed. The layer of porous alumina has a thickness of 0.7 mm and a diameter of 6.4 mm.  

With this material, the reaction according to Example 1 carried out.

4 hours after the start of the reaction, the following results are obtained:

Conversion of phenol | 82.3% Yield of 2,6-xylenol 75.1% Yield of O-cresol 7.2% Compressive strength of the mass before reaction 10.4 kg after 50 h reaction 8.0 kg after 100 h of reaction 8.0 g

example 3

There are various catalysts for the treatment of automotive exhaust and in particular for the complete combustion of carbon monoxide and hydrocarbons in the exhaust gas is known. Most of these catalysts are on porous support materials, such as silica, alumina or γ -Alu miniumoxid. This results in the disadvantages that the support material is pulverized by use in an automobile by vibration and abrasion. When applying the catalyst according to the invention, however, such disadvantages do not occur, as the experiments below show.

An ammonia solution is added dropwise to an aqueous solution Solution of a mixture of manganese nitrate and iron (III) nitrate given, wherein a mixture is precipitated. This mixture is dried and calcined at 500 ° C and contains 45 parts MN₂O₃ and 55 parts Fe₂O₃.  

100 parts of the mixture obtained are mixed with 5 parts of cellulose acetate mixed with a small amount of water. The entire mass is then kneaded and spherical Granules of the following size processed. this happens according to Example 1.

A mixture of 60 parts alumina (120 mesh per 2.54 cm) and a binder of 40 parts of lead borate glass powder and 5 parts Wheat starch and 15 parts of water are kneaded. With This material is the granules previously obtained in one Turning disk granulator coated with spraying water. After coating to a predetermined thickness becomes the coated product dried at 80-120 ° C, so then put in a jar and gradually in the oven of 200 ° C heated to 500 ° C. The product is heated to 500 ° C for 3 h held and then sintered, leaving a stable layer is obtained with a variety of fine passes.

The catalyst obtained has a core mass of Mn₂O₃ and Fe₂O₃ with 5 mm diameter and a coating of alumina glass of 0.7 mm thickness. He becomes oxidation used by hexane to determine whether the exhaust gas of an internal combustion engine is completely oxidized can be. The following reaction conditions are turned on hold.

Hexane 1% Air 99% space velocity 5000 h ^-1 , 1 atmosphere

As soon as the temperature of the catalyst bed reaches 155 ° C, begins the formation of carbon dioxide and at 230 ° C the hexane is completely converted to carbon dioxide.  

The compressive strength of the catalyst is before Reaction 13.2 kg, after 50 h of reaction 13.0 kg.

Even if the same reaction intermittently during 500 h is carried out, observed essentially no Decrease in pressure resistance. The catalyst is packed in the exhaust pipe of an automobile and this one drove over 974 km for 30 days. The compressive strength is 13.0 kg and the weight loss is extremely low.

example 4

A sample is made in which between the core and the coating there is a gap. This will be a Mixture of 50 parts walnut shell powder with a particle size of 100 meshes per 2.54 cm sieve passage, 20 parts Wheat starch, 10 parts corn starch and 30 parts water kneaded and for coating the granules according to Example 1 used, whereupon the granules continue with the Beschich coating material according to Example 1 is coated. The obtained three-layered granules are in a vessel in the same way as heated according to Example 1. You get a catalyst with a protective surface layer. The core material has a diameter of 5.5 mm, the gap has a thickness of 0.23 mm and the Surface layer has a thickness of 0.64 mm and a Outer diameter of 7.24 mm. This catalyst is used for the reaction according to Example 1 at 400 ° C. The following results are obtained:

Phenol conversion | 98.0% Yield of 2,6-xylenol 96.0% Yield of O-cresol 2.0%

example 5

Upon reaction of phenol with methanol, first O-cresol is formed and this is then converted to 2,6-xylenol. With the catalyst according to the invention the selectivity to 2,6-xylenol is improved. It is believed that the phenol up to the manganese oxide of the Core material penetrates and converted here into O-cresol whereupon the resulting O-cresol is absorbed at the core is because the passages in the coating are very narrow, so that the conversion is favored in 2,6-xylenol. When the Ab take measurements of the fine passages in the coating material, or when the thickness of the coating material is increased, the selectivity is further increased. This can be based on the difference of the yield of 2,6-xylenol at the same Conversion of the phenol when using the inventive Catalyst shown in comparison with a conventional catalyst become. This effect is especially at low conversion remarkable.

According to Example 2, the following results were obtained:

Conversion of phenol | 82.3% Yield of 2,6-xylenol 71.5% Yield of O-cresol 7.2%

On the other hand, when the manganese oxide according to Ver Example 1 is used and when a reaction temperature of 400 ° C, a space velocity of 2.61 and a molar ratio of methanol to phenol of 10 is chosen, so the following results are obtained.

Conversion of phenol | 82.0% Yield of 2,6-xylenol 50% Yield of O-cresol 32%

example 6

In the following example, the coating material is an aluminum oxide cement used. According to Example 1, a manganese oxide core manufactured. The core material is mixed with a mixture pulled, which by kneading 100 parts of aluminum oxide cement and 13 parts of water was obtained. The granules will be 2 days allowed to stand in the air, the alumina cement is hardened. The granules are then placed in a vessel and heated in the oven with raising the temperature to 620 ° C. This happens at a speed of about 100 ° C / h. The sample is then left at 620 ° C for 3 h and then cooled in the oven.

The resulting catalyst consists of spherical Globules and has powdered manganese oxide inside, while the coating is made of porous aluminum oxide cement and a thickness of 0.8 mm and a diameter of 6.6 mm Has. The physical properties are as follows compiled:

Pressure resistance | 15.7 kg Diameter of the fine passages in the coating 500-1000 Å Volume of coating fine holes 0.152 cc / g apparent porosity of the coating 46.4%.

This catalyst is used to carry out the reaction according to Example 1 used at a reaction temperature of 410 ° C. The following results are achieved:

Conversion of phenol | 31% Yield of 2,6-xylenol 27% Yield of O-cresol 4%

example 7

The core granules of manganese oxide will prepared according to Example 1. A mixture of 100 parts Diatomaceous earth and 70 parts of water are kneaded and hereby the grains obtained according to Example 1 are coated. Thereafter, the product obtained is dried at 80-120 ° C. and then in the oven at 1000 ° C at a speed of heated to about 100 ° C / h and then for 3 h to 1000 ° C be leave, whereupon the product is cooled in the oven.

The catalyst obtained consists of bodies with spherical shape and with a manganese oxide core of 5 mm Diameter and with a coating of 0.6 mm thickness Diatomaceous earth. The physical properties are summarized below:

Compressive strength | 4.0 kg Diameter of the fine passages of the coating 0.3-1.5 μm Volume of fine passages in the coating 0.564 cc / g apparent porosity of the coating 60.0%.

This catalyst is used to carry out the process according to Example 1 at a reaction temperature of 410 ° C turned puts. The following results are obtained.

Conversion of phenol | 90.0% Yield of 2,6-xylenol 83.0% Yield of O-cresol 7.0%

example 8

According to Example 1, a manganese oxide core material is produced. A mixture of 85 parts alumina (80 mesh per 2.54 cm), 12 parts kaolin, 6 parts feldspar, 5 parts walnut shells powder (60 to 100 mesh per 2.54 cm), 5 parts of wheat starch, 3 parts of cellulose acetate and 10 parts of water are kneaded and used for coating according to Example 1. The product is dried at 80-120 ° C, then in a vessel in the oven at a speed of about 100 ° C / h on a Temperature of 1200 ° C and heated for 3 h at this Keep the temperature at which the product is cooled in the oven becomes.

The resulting catalyst consists of spherical granules with a manganese oxide core with a diameter of 5 mm and with a coating of 1.0 mm thick porous Alumina. The physical properties are:

Pressure resistance | 14.3 kg Diameter of the fine pores in the coating 80-120 μm Volume of fine passages in the coating 0.25 cc / g apparent porosity of the coating 42.0%.

The catalyst is used to carry out the reaction according to Example 1 used at a temperature of 410 ° C. The following He results are achieved:

Conversion of phenol | 84.5% Yield of 2,6-xylenol 73.5% Yield of O-cresol 11.0%.

example 9

According to Example 1, a manganese oxide core material is produced. A mixture of 100 parts copper powder (80 to 150 mesh per 2.54 cm), 3 parts of cellulose acetate and 10 parts of water kneaded and according to Example 1 for coating the Kernma terials used. The product obtained is at 80-120 ° C dried and then placed in a porcelain crucible of 800 mm Internal diameter and 150 mm depth and 5 mm thickness given. The container is closed and sealed with clay. To As the clay dries, the container is placed in the electric oven heated to 1000 ° C. This happens at a speed of about 100 ° C / h. Then the container is raised for 3 hours Kept 1000 ° C and then cooled in the oven. After this Cooling the lid is removed, the product with Washed water and dried at 80-120 ° C. The obtained Catalyst consists of spherical granules with a 5 mm diameter manganese oxide core material and with a coating of 0.8 mm thickness of porous copper. The physical properties of the composition are as follows:

Pressure resistance | 27,30 kg Diameter of the fine pores in the coating 3-6 μm Volume of fine pores in the coating 0.078 cc / g apparent porosity of the coating 36.8%.

This catalyst is used to carry out the reaction according to Example 1 used at a reaction temperature of 450 ° C. you achieves the following results:

Conversion of phenol | 39% Yield of 2,6-xylenol 16% Yield of O-cresol 23%.

Claims (1)

A catalyst with a surrounding and against mechanical destruction protective porous coating of sintered anor ganic material, obtainable by applying the coating to the catalyst under heating, characterized in that a catalyst coated with a ver combustible organic material or that a powdered catalyst with a combustible organic material is mixed and then formed, that the product obtained with a combustible organic material, an inorganic powder and optionally a binder-containing coating material is coated and that the coated product to a sintering or melting of the powdered inorganic material and optionally the binder and heated sufficiently high temperature to burn the combustible organic material.